This invention relates to an air intake device.
The invention applies generally to the naval (or nautical) sector and, more specifically, to the production of military submarines, where these devices are universally known as snorkels.
In this description the term “snorkel” and its definition as “air intake device” will be used without distinction.
Still more specifically, the invention relates to an air intake device or snorkel combined with one or more other devices.
In conventional military submarines, the snorkel is designed to allow the submarine to remain hidden as far as possible, even during the recharging of the batteries used for submarine propulsion.
In effect, the snorkel is basically a tube that pierces the sea surface while the submarine is navigating below the surface but at a shallow depth (usually referred to as “snorkel depth” or “periscope depth”), in order to guarantee the supply of air necessary for operation of the internal combustion engines used to recharge the batteries, as well as for ventilation of the submarine quarters.
Although, in actual fact, snorkel depth and periscope depth may be slightly different, the term “periscope depth” will hereinafter be used in a general sense to refer to both periscope depth and snorkel depth without distinction.
The possibility of allowing only a tube, and not a bulkier part of the submarine, to emerge above the surface reduces the risk of detection during these operations, when the submarine is particularly vulnerable to enemy attacks.
The snorkel is therefore mounted and housed in a mast rising up above the water surface from the submarine hull in a substantially vertical direction during navigation at periscope depth.
Besides the snorkel, raising other devices, sensors and/or antennas, used for viewing and/or communication purposes, above the water's surface while keeping the boat as hidden as possible below the surface is a well-known need in the field of submarine design.
In this regard, it is known from document DE 195 35 873 the use of retractable masts provided of a vertical hydraulic cylinder having a piston rod vertically movable, a mast rod (having a profile generally favourable to the water flow) fixed to the piston rod and a generally known information device (for example a sensor or a radar) mounted on the upper end of said mast rod.
The retractile masts described in document DE 195 35 873 can also be used, alternatively to the lifting of information devices, with a snorkeling function.
Disadvantageously, as it can be simply understood, in the above kind of lifting devices (as in the majority of the known lifting devices) the number of retractile masts linearly increases with the enhancing of the devices number, in particular considering that at least one mast must be dedicated to the snorkeling function.
It is to be noted that the presence of an high number of elevated masts, not only makes the submarine easier to locate because their actual presence is visible but also has the disadvantage that, on piercing the water's surface, they create swirling near the surface and produce a mass of white water (or foam) and leave a clearly visible trail in their wake.
To limit the negative effects of this disadvantage, these devices and mechanisms have been combined with the sensors/antennas necessarily present on the submarine in such a way as to limit not only the number of parts moving above the surface but also their size.
In this regard, prior U.S. Pat. No. 7,209,288 deals with the problem by providing a snorkel device furnished not only with a snorkel tube proper but also with two compact units, one associated with optical observation means and the other with generic communications means. Both compact units are equipped with respective drive means.
The solution proposed by U.S. Pat. No. 7,209,288 is not itself free of disadvantages because the snorkel tube has to accommodate two additional drive systems, besides that of the snorkel itself, thus increasing the size of the part of the submarine that emerges above the water's surface during navigation at periscope depth.
In effect, the presence of the drive systems inside the mast that houses the snorkel necessarily implies increasing the size of the mast, which in turn means increasing the negative effects of water turbulence and wake formation.
A further drawback connected with the solution proposed in U.S. Pat. No. 7,209,288 is due to the fact that the permanent presence of the communications means in the snorkel mast makes it necessary to extend the snorkel mast even when only the communications means need to be used, thus producing a considerable wake even in situations where this is not strictly necessary.